Active implantable medical devices can be placed in a particular configuration so as to ensure data exchange with an external apparatus (often called a “programmer”), allowing to verify parameterization of the implanted device, read the data recorded thereby, notably the data of the “Holter” type intended to an a posteriori statistical analysis of cardiac activity over a long duration, or to write (i.e., record) some data into the device's memory, notably to reprogram or update the implanted device software and/or firmware.
The present invention is more particularly directed to the circumstances when the data exchange between said implanted device and external apparatus is operated by means of varying the magnetic field produced by an induction coil, a technique that is known by a person of ordinary skill in the art as an “induction process”. The electromagnetic coupling between the implanted device and the external apparatus is therefore essentially a magnetic coupling, with the implanted device and the external apparatus having therefore so-called “wave collectors” in the form of similar coils that shall be positioned facing one another so as to ensure proper magnetic wave coupling.
Coupling of the external apparatus with the implanted device is usually performed by the practitioner who is operating the external apparatus, who uses a device called a “programming head” or “telemetry head” in the form of a housing containing the coil of the external apparatus (programmer), as well as associated electronic circuits. The telemetry head is connected to the external programmer by means of a cable. The practitioner has to move the telemetry head above the patient's body in the region where the implanted device has been implanted, until the position leading to the highest (or at least a minimum acceptable) signal level is located: that means that the telemetry head is positioned right in front of the implanted device, which ensures optimal coupling. Then the practitioner can go forward and proceed to initiate the data exchange between the implanted device and the programmer, while maintaining the telemetry head at the position thus determined.
The search for optimal coupling is a determining factor, not only toward the quality and reliability of the exchange of signals between the implanted device and the external apparatus, but also in order to reduce the current consumption of the emitting circuits of the implanted device, therefore increase the longevity of the latter: indeed, an imperfect coupling requires a higher transmission power, and therefore induces a higher energy consumption of the implant.
The operating mode described above is typically practiced by all practitioners during a patient office visit to a practitioner following implantation of the device.
It can however be desirable, notably thanks to the new communication media (Internet, GPRS, UMTS, . . . ) to ensure a remote follow-up of the patient and home-monitoring, without any intervention by the practitioner. More advantageously, it can also be desirable to perform this follow-up at regular time intervals, for example, with a daily data recovery and teletransmission towards a remote telesurveillance server, so as to ensure a much closer or more frequent surveillance of the patient's health status, while avoiding multiple office visits with the practitioner.
The practitioner being not present, the implementation of the external device implies the patient's direct involvement to effect the data exchange.
One problem with this is the necessity to properly position the wave collector of the external device relatively to the implanted device, so as to ensure optimal coupling between these two elements of the telemetry system. It is not desirable that the patient himself searches for the optimal positioning whenever the implanted device needs to be interrogated: In addition to the time wasting in attempts and the difficulty for an inexperienced person to find the optimal coupling, the patient may present a loss of autonomy that could not allow him to perform this operation.
It also should be understood that the search for optimal coupling of the wave collector is a relatively tedious operation for an inexperienced person: the wave collector of the external device is an antenna with a diameter around 5 cm, that shall be centered in front of the implanted device, which has a wave collector having a diameter around 2 cm, and that shall be done with an accuracy of about 1 cm so as to ensure a satisfactory optimal coupling.
Furthermore, this precise positioning must be maintained throughout the complete duration of the operation (interrogating an implanted device can last several minutes), with a lack of coupling inducing a risk to lead to a loss of information obliging one to repeat or start over again some interrogation sequences.
Some clothes comprising built in antennae are already known in the prior art: see for reference, patents U.S. Pat. Nos. 6,590,540, 6,483,469 or 6,680,707. However, these patents disclose radiofrequency antennae for communication with a different type of equipment, for example, a radio transmitter or a radiocommunication base station. Also, these disclosures do not concern with a telemetry process implementing an induction process, and do not recognize that there is a need for the precise positioning of the antenna onto the patient's body, and positioning of the antenna is not a determining parameter. These documents therefore do not address the problem that is specific to the present invention, which is correlated to the very close proximity between the respective wave collectors of the implanted device and the external apparatus.